I have looked into this and as far as I can tell this is more of a myth than anything else. The only discussion regarding this on that other forum and when you dissect the thread most of it is meaningless.
Whatever the reasons were behind Marantz revising the amplifiers in 240/250/1200's we will never truly know. The revisions in the earliest models were likely due to problems that were encountered once these models were in the field.
Hi Chris,
My message was meant to draw you and Jk out on this topic. Glad to see BK interested as well. While I'm first and foremost a fan of the Model 500, especially when operating up to its maximum potential (thank you Jk). For most applications the Model 510/510M does a pretty good job approximating the 500, except when one is driving a difficult speaker load OR listening very critically. (Thanks again Jk).
As everyone seems to be suggesting, and especially because the Model 250 already outperforms its specs, why mess with success? Yah, I get that, BUT...
There is a considerable gap up in price, and worse still, availibility between the Model 250 compared to either the Model 300DC or 510/510M. Even the 250 is starting to be scarce.
Jk hit on the issue. My understanding is that, in the design of the Model 250, Marantz used more transformer than would have been necessary, especially based on the Amp board design itself. As a result, when operating within stated specs, the 250 exhibits no issues at all.
Great, but who monitors that they are operating within spec while listening to music... not me.
The imbalance in the amp, when being pushed, can apparently have some unexpected, nasty consequencies. Of course, with a lesser transformer, that was a better balance with the Amp board, this instability would never happen, at least at as high an output level, a la 175+W/ch-RMS.
QUESTION 1: What owner of a carefully refurbed Model 250 wants to be concerned about this potential instability when listening at concert volume levels the next time a loud transient comes along in the music? ... and Oops!
Oops! is not a satisfactory situation... not with an amp of this caliber.
Especially, as Jk has suggested, the imbalance which leads to this instability at higher output levels is not so difficult to understand. Easy for me to say.
QUESTION 2: Can we engineer a fix to reign in this instability before it causes problems; or, better still, in such a way as to allow the Amp board to more fully take advantage of the extra transformer headroom, in effect making the 250 a bigger amp, and yet maintain a balance and avoid the present instabilities at high output. Yes we already have the Model 510/510M and the 500; but they are quickly being bid up in price such that they are no longer an option to many AKers.
Personally, I'm a fan of HI-FI. That means that you don't squeeze down the transients in the music with an amp that just can't quite cut the mustard.
QUESTION 3: Who cares. Do we really want to tackle this problem?
You know my answer. But that's just me, and I'm no engineer.
